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November 24, 2008

Wheat yields could fall 50% by 2040 as world phosphorus runs out

by Sarah Dryden

Yields of non-organic wheat could fall from an average of 9 tonnes a hectare to 4 tonnes a hectare sometime between 2040 and the end of this century as the planet runs out of phosphorus, a key part of the fertiliser needed to grow non-organic crops.

85% of the known deposits of phosphorus are in four North African countries: Morocco, Algeria, Tunisia and Egypt. The world is using the 4 to 8 billion tonnes of phosphorus left at the rate of around 125 million tonnes a year.

Research by the University of Newcastle, under the EU's Quality Low Input Food Programme, shows that yields of non-organic wheat can drop to well below organic yields from nearly 8 tonnes a hectare to 2.5 tonnes a hectare without phosphate fertiliser. These estimates are based on expected yield reductions, if no further phosphates are applied from 2070 for 30 years.

Organic yields without phosphate would be 6 tonnes a hectare. The price of mineral rock Phosphate has increased by more than 500% over the last two years. Over the last 40 years, use of nitrogen, potassium and phosphate fertiliser has increased by 5 to 7 times, but yields have only doubled. So crops use fertiliser 2 to 3 times less efficiently now compared to 40 years ago.
This is in part because breeding for conventional farming has produced varieties with smaller root systems, and because the microbes in the soil which help plants use fertiliser efficiently are inhibited by the use of artificial fertiliser.

At the Soil Association's National Conference - Food and Farming in 21st Century Britain - Professor Carlo Leifert said "For the last 50 years industrial farming has been relying on phosphate mined in North Africa in ever-increasing quantities, while using this scarce resource less and less efficiently. Scarcity of phosphates are driving up the price, and sooner or later, as we inevitably start to run out of phosphates, non-organic yields will start a dramatic decline. Organic farming will also face problems, although not on the same scale, and the solution would be for organic farmers to use human sewage as fertiliser."

Peter Melchett, Policy Director of the Soil Association said "The Secretary of State for the Environment, Hilary Benn, said at the Soil Association Conference that 'fossil fuels will eventually run out' and that the Government are now committed to making 80% cuts in greenhouse gas emissions. The new threat of phosphate shortages and yield losses add to the urgency of moving our food production from a reliance on imported oil, gas and phosphates, and reliance on artificial nitrogen fertiliser."

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